ROME (Reuters) - Italians voted on Sunday in one of the most closely watched and unpredictable elections in years, with pent-up fury over a discredited elite adding to concern it may not produce a government strong enough to lead Italy out of an economic slump.

The election, which concludes on Monday afternoon, is being followed closely by investors; their memories are still fresh of the potentially catastrophic debt crisis that saw Mario Monti, an economics professor and former bureaucrat, summoned to serve as prime minister in place of Silvio Berlusconi 15 months ago.

A weak Italian government could, many fear, prompt a new dip in confidence in the European Union's single currency.

Opinion polls give the center-left a narrow lead but the result has been thrown completely open by the prospect of a huge protest vote against the painful austerity measures imposed by Monti's government and deep anger over a never-ending series of corruption scandals. Berlusconi's centre-right has also revived.

"I'm not confident that the government that emerges from the election will be able to solve any of our problems," said Attilio Bianchetti, a 55-year-old builder in Milan, who voted for the anti-establishment 5-Star Movement of comic and blogger Beppe Grillo.

The 64-year-old Grillo, heavily backed by a frustrated generation of young Italians hit by record unemployment, has been one of the biggest features of the last stage of the campaign, packing rallies in town squares up and down Italy.

"He's the only real new element in a political landscape where we've been seeing the same faces for too long," said Vincenzo Cannizzaro, 48, in the Sicialian capital Palermo.

Italians started voting at 8 a.m. (0700 GMT). Polling booths will remain open until 10 p.m. on Sunday and open again between 7 a.m. and 3 p.m. on Monday. Exit polls will come out soon after voting ends and official results are expected by early Tuesday.

Snow in northern regions is expected to last into Monday and could discourage some of the 47 million people eligible to vote in Italy to head out to polling stations, though the Interior Ministry has said it is fully prepared for bad weather.

Monti and his wife cast their votes at a polling booth in a Milan school on Sunday morning and centre-left leader Pier Luigi Bersani, the leader opinion polls suggest will have to form a new government, voted in his home town of Piacenza.

A small group of women's rights demonstrators greeted former prime minister Berlusconi when he voted in Milan. They bared their breasts in protest at the conservative leader, who is on trial at present for having sex with an underage prostitute.

Whichever government emerges from the election will have to tackle reforms needed to address problems that have given Italy one of the most sluggish economies in the developed world for the past two decades.

But the widespread despair over the state of the country, where a series of corruption scandals has highlighted the stark divide between a privileged political elite and millions of ordinary Italians, has left deep scars.

"We're all about getting favors when we study, getting a protected job when we work. That's the way we are and we can only be represented by people like that as well," she said.

FRUSTRATION

Final polls published two weeks ago showed center-left leader Bersani with a 5-point lead, but analysts disagree about whether he will be able to form a stable majority that can make the economic reforms they believe Italy needs.

While the center left is still expected to gain control of the lower house, thanks to rules that guarantee a strong majority to whichever party wins the most votes nationally, a much closer battle will be fought for the Senate, which any government also needs to control to be able to pass laws.

The euro zone's third-largest economy is stuck in deep recession, struggling under a public debt burden second only to Greece in the 17-member currency bloc and with a public weary of more than a year of austerity policies.

Bersani is now thought to be just a few points ahead of media magnate Berlusconi, the four-times prime minister who has promised tax refunds and staged a media blitz in an attempt to win back voters.

Think-tank consultant Mario, 60, who was on his way to vote in Bologna, said Bersani's Democratic Party was the only serious grouping that could help solve the country's economic woes.

"They're not perfect," he said. "But they've got the organization and the union backing that will help them push through the structural reforms."

A strong fightback by Berlusconi, who has promised to repay a widely hated housing tax, the IMU, imposed by Monti last year, saw his support climb during a campaign that relentlessly attacked the "German-centric" austerity policies of the former European Union commissioner.

"I won't vote for Monti, and I don't think a lot of people will. He made a huge blunder with IMU," said 35-year-old hairdresser Marco Morando, preparing to vote in Milan.

But the populist frustration Berlusconi's campaign tapped into has also benefitted Grillo and many pollsters said his 5-Star Movement, made up of political novices, was challenging the center-right for the position as second political force.

"I'm very worried. There seems to be no way out from a political point of view, or from being able to govern," said Calogero Giallanza, a 45-year-old musician in Rome, who voted for Bersani's Democrats.

"There's bound to be a mess in the Senate because, as far as I can see, the 5-Star Movement is unstoppable."